Start a simple Slic3r::Log to collect all of the debugging prints to a single area.

Upgrade backend to boost::log as needed.

xs/src/libslic3r/Log.hpp

@@ -0,0 +1,24 @@
+#ifndef slic3r_LOG_HPP
+#define slic3r_LOG_HPP
+
+#include <string>
+
+namespace Slic3r {
+
+class Log {
+public:
+    static void fatal_error(std::string topic, std::wstring message) {
+        std::cerr << topic << ": ";
+        std::wcerr << message << std::endl;
+    }
+
+    static void info(std::string topic, std::wstring message) {
+        std::clog << topic << ": ";
+        std::wclog << message << std::endl;
+    }
+
+};
+
+}
+
+#endif // slic3r_LOG_HPP